Re: [RFC v2 1/2] ppc/fpu: Add generic FPU api similar to x86

+
+/*
+ * Use kernel_fpu_begin/end() if you intend to use FPU in kernel context. It
+ * disables preemption so be careful if you intend to use it for long periods
+ * of time.
+ * TODO: If you intend to use the FPU in irq/softirq you need to check first with
+ * irq_fpu_usable() if it is possible.

Please avoid the overly lone lines comments.

+extern bool kernel_fpu_enabled(void);
+extern void kernel_fpu_begin(void);
+extern void kernel_fpu_end(void);

No need for the externs.

+/*
+ * Track whether the kernel is using the FPU state
+ * currently.

This all fits on a single line.

+static bool fpu_support(void)
+{
+	if (cpu_has_feature(CPU_FTR_VSX_COMP)) {
+		return true;
+	} else if (cpu_has_feature(CPU_FTR_ALTIVEC_COMP)) {
+		return true;
+	} else if (!cpu_has_feature(CPU_FTR_FPU_UNAVAILABLE)) {
+		return true;
+	}

No need for the braces, or else after a return.  In fact this could
be simplified down to:

	return cpu_has_feature(CPU_FTR_VSX_COMP) ||
		cpu_has_feature(CPU_FTR_ALTIVEC_COMP) ||
		cpu_has_feature(CPU_FTR_FPU_UNAVAILABLE));

+	preempt_disable();
+
+#ifdef CONFIG_VSX
+	if (cpu_has_feature(CPU_FTR_VSX_COMP)) {
+		enable_kernel_vsx();
+		return;
+	}
+#endif
+
+#ifdef CONFIG_ALTIVEC
+	if (cpu_has_feature(CPU_FTR_ALTIVEC_COMP)) {
+		enable_kernel_altivec();
+		return;
+	}
+#endif
+
+#ifdef CONFIG_PPC_FPU
+	if (!cpu_has_feature(CPU_FTR_FPU_UNAVAILABLE)) {
+		enable_kernel_fp();
+		return;
+	}
+#endif

All the features are defined away if not supported (and we already rely
on that in fpu_support()).  So this could become:

	if (cpu_has_feature(CPU_FTR_VSX_COMP))
		enable_kernel_vsx();
	else if (cpu_has_feature(CPU_FTR_ALTIVEC_COMP))
		enable_kernel_altivec();
	else if (!cpu_has_feature(CPU_FTR_FPU_UNAVAILABLE))
		enable_kernel_fp();

Same for the disable path.